Power supply for plural motor interlock systems



Sept. 22, 1936. c FARRAND 2,655,124

POWER SUPPLY FOR PLURAL MOTOR INTERLOCK SYSTEMS Filed April 18, 1935 V 3Sheets-Sheet l FlEr 1 INVENTOR Clair L. Farrand BY fi ATTORNEY Sept. 22,1936.

c. L. FARRAND 2,055,124 POWER SUPPLY FOR PLURAL MOTOR INTERLOCK SYSTEMSFiled April 18, 1935 s Sheets-Sheet 2 f 11.2. FlEr E INVENTOR Clair L.Farrand BY Ma/fl/MW ATTORNEY 1 Sept- 1936- c. L. FARRAND I 2,055,124

POWER SUPPLY FOR PLURAL MOTOR INTERLOCK SYSTEMS Filed April 18, 1955 3Sheets-Sheet 3 INVENTOR.

Clair L. Farrand BY W KAZMM A TTORNEY Patented Sept. 22, 1936 UNITEDSTATES PATENT OFFICE POWER SUPPLY FOR PLURAL MOTOR INTERLOCK SYSTEMSApplication April 18,

9 Claims.

and reproduction of sound waves that perfect recording and reproductioncan only be obtained by maintaining a constant linear velocity for therecord carrier since sound is made up of one or more frequencies havinga definite wave form and relationship to one another both as toamplitude and phase. Any disturbance of that relationship during thetranslation from acoustic to electrical energy, or vice versa, producesdistortion, one of the chief causes being variation in speed of thedriving means. An object of the invention, therefore, is to efiicientlyprogress a linear carrier of sound waves at constant speed.

Where the record carrier is a film, and recording is accomplished by theprojection thereon of modulated light, while reproduction isaccomplished by the projection thereon of constant intensity light, theapparatus required employs a plurality of driving sprockets, supply andtakeup reels. In addition, since it is customary to have on thediapositive, pictures of concomitant sound sources the projection ofwhich is accomplished simultaneously with reproduction of sound, thereis associate apparatus being simultaneously driven, this apparatusproducing variations in load on the driving means which are generallyelectrical motors of the synchronous type. A further cause of speedvariations where motor power is used is the variation in the motorsupply energy. Another object, therefore, of this invention is to drivea talking motion picture film past a sound translation point at aconstant speed regardless of variations in speed of other moving parts.

The present invention contemplates the use of separate motors fordriving different parts of the system. In brief, a constant speedsynchronous motor of special construction is employed for progressingthe film past the translation point while the usual type of synchronousmotor may be employed for driving the sprockets feeding the film to andfrom the translation point, the supply and take-up reels, and, whenreproducing, the picture projecting mechanism. In accordance with thisinvention these separate motors, which would if operated separatelyrequire different 1935, Serial No. 17,099

times to reach synchronous speed, are arranged to operate independentlywhen in synchronism within certain predetermined limits, thus permittingone motor to vary in speed without disturbing the other within theselimits. This arrangement also permits the motors to start and stoptogether and thereby retain their synchronous relationship at all times.The special constant speed synchronous motor is directly connected tothe drive sprocket which controls the speed of the film past thetranslation point while the other motor may be coupled by gears, chains,belts, or the like, to the other moving parts. A back lash coupling orinterlock provides the synchronous independence of the motors but doesnot permit them to slip an entire pole. The coupling device itself is ofthe mechanical type which may be adjusted to provide for different polepitches of different motors.

The invention will be better understood from the following descriptionread in conjunction with the accompanying drawings in which Fig. 1 is adiagrammatic arrangement of the power supply for sound recording units,

Fig. 2 is a dagrammatic view of a picture projecting and soundreproducing unit supplied with power in accordance with the invention,

Fig. 3 is an end View of one of the motors of Figs. 1 and 2 showing therelationship between the coupling device and the motor, and

Fig. 4 is a cross sectional view of the coupling device.

In Fig. 1 two sound systems A and B are shown for the purpose ofillustrating that a plurality of units may be satisfactorily operatedfrom a single energy supply. Units A and B being identical, the samenumerals have been given to like elements. The motor 5 is directlyconnected to a sprocket i over which a film i? is driven past atranslation point which may be on the sprocket itself or at a pointimmediately adjacent thereto in the form of a flat or curved gate. Feedsprockets 9 and lil progress the film to and from the sprocket J in thewell known manner. The sprockets 9 and iii are geared to a drive shaftl2 directly connected to a motor 6 of the usual synchronous type. Theshaft i2 is also geared to a shaft 55 which drives a take-up reel forthe film ll. A mechanical back lash coupling or interlockl9 shown indetail in Figs. 3 and 4 couples a shaft 20, geared to shaft l2, with theshaft of motor 5.

The system just described is claimed and more fully disclosed in myco-pending application Serial No. 17,098 filed April 18th, 1935, whilethe special type of constant speed motor is disclosed and claimed in myco-pending application Serial No. 17,097 filed April 18th, 1935. Thepresent invention relates specifically to the energy supply for themotors 5 and 6 which will now be described.

As was pointed out in my co-pending application Serial No. 17,098 filedApril 18th, 1935, mentioned above, there are several causes of speedvariations in the motor 5. One is faulty and unbalanced construction ofthe motor 5 which has been overcome by the invention in co-pendingapplication Serial No. 17,097 filed April 18th, 1935. The second is thatvariations in load caused by varying resistance at different pointswithin the system are transferred to the motor and this problem has beensolved by the subject matter disclosed and claimed in my copend-' ingapplication Serial No. 17,098 filed April 18th, 1935. The third cause isthat variations in the commercial power supply occur which vary thespeed of the motor and the elimination of this cause forms the subjectmatter of the present application.

Referring'now to the power supply the units A and B, all energy isreceived over conductors 39 from the usual commercial source which mayvary in voltage. This energy is utilized to operate a commercialthree-phase motor 32 flexibly connected by a resilient viscouslydampened coupling 33 to a large capacity three-phase generator 35stabilized by a flywheel 35. The coupling 33 and flywheel 35 cooperateto provide the rotor or motor 35 with a substantially constant speed ofrotation in spite of the fluctuations in voltage on the commercial line30. The generator 35 will now provide a much stabler energy output tothe motor 5 to which it is connected than would otherwise be obtainablefrom the lines 35. The field of the motor 5 is supplied from a D. C.source.

The motor 5 may be driven directly from the main supply leads 30 anyvariations in speed thereof being prevented from affecting the motor 5by the coupler l9 which permits independent operation of the motorswithin a pole pitch of motor 5 as disclosed in co-pending applicationSerial No. 17,098 filed April 18th, 1935. The motor 5, therefore, isisolated not only from variations in speed of the motor 6 caused byvariations in the load, but also from variations in the power suppliedto the motor 6. This constant energy supply to the motor 5, plus itsspecial construction, its constant load, and its isolation from thedriving and driven elements of the remainder of the system, permits themotor 5 to have a constancy of speed which is not obtainable with otherdriving systems known in the art.

As the generator 34 has a large output capacity relative to the loadprovided by the motor 5, several units may operate in parallel withoutdisturbing its output characteristics. Switches 40, ll, 52 and 33 areemployed for operating any unit desired independently or simultaneouslywhile the switch 44 serves the motor generator sets 32 and 34. The fieldof the generator 35 may be supplied from a direct current source asshown.

Referring now to Fig. 2, a picture projection unit 59 may be supportedon top of a plate 5| -mounted on standard 53, a sound reproducing unit54 being supported below plate 5i, the two units being aligned tofacilitate the progressing of a sound and picture film record 55 fromsupply reel 56 to take-up reel 57. The sound head 54 may be the same asthe unit shown in my co-pending application Serial No. 17,098 filedApril 18th, 1935.

A special constant speed motor represented by the dotted line 59 isdirectlyconnected to a sound reproducing sprocket 59 and controls thespeed of the film 55 past the sound translation point which in this caseis on the sprocket B9. A light source 52, optical units 63, and lightsensitive device 5 with their controls 95 and meter 96 are otheressential units of the sound unit 54. A synchronous motor 68 directlydrives through a shaft 79 the sprockets and pull-down mechanism in theprojector 59, the drive sprockets in the sound unit 55, and take-up reel57.

The general power for the system is obtained over main conductors 72,which are shown as a three wire two or three phase system but which mayalso be single phase, the motor 68 being connected thereto through aswitch 73. The conductors 72 also directly supply a synchronous motor 15resiliently coupled to a threephase generator '16 by a resilientviscously damped coupling 77, a heavy flywheel "l8 stabilizing therotational speed of the rotating elements and thus the energy output.The field of the generator 75 is supplied with direct current. As shown,the power energy for the special synchronous motor 59 is supplied fromgenerator 76 through switch 79 and thus this motor has a source ofenergy considerably more stable than that obtainable from lines 32 sinceit is not subject to small variations which occur on the lines 72. V

The power supply system of Fig. 2, therefore, functions to preventvoltage fluctuations on main line 72 within certain limits fromafiecting the linear velocity of the film record past the soundtranslation point in the reproducer 5 5.

The combination of the special constant speed motor 59, the back lashcoupler l9 interconnecting the motors 59 and 58, and positioned behindthe motor 59 as illustrated in Fig. l, and the motor generator unit'i5l5, function to provide a drive for the reproducer 54 and projector50 which maintains synclironism between the various driven elementswhile giving the film relatively constant speed past the soundtranslation point.

Referring now to Figs. 3 and .4 the coupler l9 comprises two concentricplates 85 and Bl on shaft 29 adjustable with respect to one another, anda disc or plate 82 mounted on the shaft of motor 5, the disc 82 havingpin extensions 83 and 84 diametrically opposite one another on the disc.The plates 89 and BI are maintained in their adjusted position by meansof screws 85. The desired adjustment between the plates 80 and 8| issuch that the variation between the shaft 20 and the shaft of motor 5 isjust less than one pole pitch of the motor 5.

As described in the above mentioned co-pending application, the motor'5has forty (40) poles, as shown at 87, and 120 armature teeth, as shownat 85. In Fig. 3 the pole pitch is represented by the angle alpha andthis angle should be greater than twice the angle theta or the angleformed between the pin 84 and plates 80 and 8!, assuming pin 84 to be acentral position.

This adjustment of the plates 80 and 8| will prevent any variation inspeed between the two motors greater than one pole pitch andconsequently prevent the slippage of the motors out of synchronism whilepermitting relatively independent variations in speed therebetweenwithin these limits. This provides a system wherein the motor is notsubjected to speed variations of motors 6 within a. pole pitch of motor5 in Fig. 1 or the motor 59 is not subjected to the same speedvariations in motor 68 in Fig. 2. The constant speed sprockets 'l and 60are thus isolated within limits from motors 6 and 68 respectively.

What is claimed is:

1. In a system for progressing a record carrier past a translation pointat a constant speed, a film driving system comprising a motor, asprocket directly connected to said motor for progressing film past atranslation point, sprockets for feeding film to and from said firstsprocket, a motor directly connected to said feed sprockets, a powersupply for said second motor, a motor-generator set energized from saidpower supply, means for connecting said first mentioned motor to saidmotor-generator set, and means for stabilizing the rotation of thegenerator of said motor-generator set.

2. In a film drive system, the combination of a main power supply havingenergy fluctuations therein, a motor generator set, a motor for drivingcertain mechanism of said system, a motor for driving film past a soundtranslating point, said first motor being supplied with energy directlyfrom said main power system, and said second motor being supplied withenergy from said motor-generator set supplied from said main powersupply, and means for maintaining a constant energy output from thegenerator of said motor-generator set during fluctuations of said mainpower supply.

3. In a system for driving difierent loads one of which is to have aconstant speed, the combination of individual motors for each of saidloads, a power source connected to said motor adapted to drive the loadwhich may be permitted to vary in speed, a motor generator setinterposed between said power source and said motor adapted to drivesaid constant speed load, and means for maintaining the generator ofsaid motor generator set at a substantially constant speed duringfluctuations in speed of the motor of said set.

4. In a system for operating a portion of a rotating system at aconstant speed, the other portion of said system having a permissiblevariation therein, the combination of a separate motor for each of saidportions, a mechanical coupling device between said motors permitting apredetermined slippage therebetween within limits of a pole pitch of oneof said motors, a motor-generator set, means for providing the generatorof said motor-generator set with a substantially constant output, andmeans for supplying the motor of said motor-generator set and one of themotors of said system directly from a common power supply.

5. In combination, a plurality of motors for driving different loads,two of said motors being mechanically interconnected and adapted to bedisconnected when operating in synchronism, a generator connected to oneof said motors and having means for maintaining a constant speedthereof, a motor for driving said generator, and a common alternatingcurrent supply means for the other of said first mentioned motors andsaid last mentioned motor.

6. In a drive system for motion picture film, a translating point, adrive sprocket for progressing said film past said translation point,sprockets for progressing film to and from said drive sprocket, a motordirectly connected to said drive sprocket, a second motor directlyconnected to said feed sprockets, an interlocking device between saidmotors to permit independent operation within a pole pitch of one ofsaid motors, a power supply, a motor-generator set, means for connectingsaid second mentioned motor and the motor. of said generator set to saidpower supply and the generator of said motor-generator set to said firstmentioned motor, and means for maintaining the energy output of thegenerato of said motor-generator set substantially constant.

7. A system in accordance with claim 6 in which the motor and generatorof said motor-generator set are interconnected by a resilient couplingand the rotating parts of which are under control of a flywheel.

8.In a system for driving portions of an interconnected load at arelative constant speed compared with other portions of said load, amain power supply having energy fluctuations therein, a motor-generatorset interconnected by a flexible coupling, a flywheel mounted on therotating elements of said motor-generator set, a motor for driving theportion of said load having relative constant speed, means forconnecting the generator of said motor-generator set to said motor, asecond motor for driving the other portion of said load, and means forconnecting the power supply to the motor on said motor-generator set andsaid second motor.

9. A system in accordance with claim 8 in which said loads aremechanically interconnected when the variation in speed between themotors driving said portions of said load is greater than the pole pitchof one of said motors.

CLAIR L. FARRAND.

